GAIN CONTROL AMPLIFIER
Systems, methods, and devices provided herein are directed to improvements in gain control amplifiers that receive an input signal and generate an output signal with a selectively variable gain. A differential amplified gain stage receives an input signal and scales the input signal to generate a scaled signal. A gain adjust stage receives the scaled signal and an adjust signal and adjusts an amplitude of the scaled signal based on the adjust signal to generate an adjusted scaled signal. The adjusted scaled signal has a substantially constant impedance regardless of value of the adjust signal.
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This invention was made with Government support under subcontract 02ESM162076 awarded by General Dynamics. The Government has certain rights in the invention.
TECHNICAL FIELDThe invention relates to gain control amplifier circuits.
BACKGROUNDIn many communications system, e.g. radio frequency (RF) communications systems, it is desirable for a signal receiver to scale, or apply a gain to, an incoming signal for further processing or subsequent retransmission of the signal. Because an amplitude of an incoming signal may vary, it is also desirable to implement circuits that apply a selectively adjustable gain to an input signal. Such circuits may be referred to as gain control amplifiers. Gain adjustment may cause undesirable limitations on signal bandwidth, specifically at high frequencies.
SUMMARYThis disclosure is directed to improvements in gain control amplifiers. Various examples described herein enable amplification of a signal with beneficial performance across a large bandwidth, including at high frequencies. In some aspects, examples described herein may provide for a gain control amplifier that outputs a scaled signal with a substantially constant impedance, regardless of a level of scaling applied to a signal by the amplifier. In other aspects, examples described herein may provide for a gain control amplifier that outputs a scaled signal at a substantially constant impedance across a large bandwidth of frequencies. In still other aspects, examples described herein may provide for a gain control amplifier that operates with minimized power dissipation.
In one example, an amplifier device is described herein. The amplifier device includes a differential amplifier gain stage that receives an input signal and applies a gain to the input signal to generate a scaled signal. The amplifier device further includes a gain adjust stage that receives the scaled signal and an adjust signal and adjusts an amplitude of the scaled signal based on the adjust signal and outputs an adjusted scaled signal. The adjusted scaled signal has a substantial constant impedance regardless of a value of the adjust signal.
In another example, a method is described herein. The method includes receiving, at a differential amplifier stage, an input signal. The method further includes scaling, by the differential amplifier stage, the input signal to generate a scaled signal. The method further includes receiving, at a gain adjust stage, the scaled signal. The method further includes receiving, at the gain adjust stage, an adjust signal. The method further includes adjusting an amplitude of the scaled signal by the gain adjust stage. The method further includes outputting an adjusted scaled signal, wherein the adjusted scaled signal has a substantially constant impedance regardless of a value of the adjust signal.
In another example, a device is described herein. The device includes means for scaling an input signal to output a scaled signal. The device further includes means for receiving the scaled signal and an adjust signal. The device further includes means for adjusting an amplitude of the scaled signal based on the adjust signal. The means for adjusting an amplitude of the scaled signal output an adjusted scaled signal with a substantially constant impedance regardless of a value of the adjust signal.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Amplifier 2 includes a differential amplifier stage 4 and a gain adjust stage 6. Differential amplifier stage 4 may receive an input signal 12. Input signal 12 may be a differential input signal, where the input signal is represented by two signals of opposite polarity, e.g. a positive input signal and a negative input signal. Differential amplifier stage 4 may apply a gain to an input signal 12, and output a scaled signal 14. The scaled signal 14 may be amplified (gain of greater than unity) or attenuated (gain of less than unity). In one example, the scaled signal 14 is a differential signal.
Gain adjust stage 6 may receive the scaled signal 14, adjust an amplitude of the scaled signal 14, and output an adjusted scaled signal 18. As also shown in
Gain adjust stage 6 may output adjusted scaled signal 18. Adjusted scaled signal 18 may define a substantially constant impedance. In one example, gain adjust module 6 may output an adjusted scaled signal 18 that defines a substantially constant impedance regardless of a level of amplitude adjustment of gain adjust stage 6.
The gain of amplifier 2 may be selectively adjusted via adjust signal 22. In one example, the gain of amplifier 2 may be manually adjusted by a user. In another example, although not depicted herein, amplifier 2 may include additional circuitry, programmable logic, or other devices that detect amplitudes of signals input to amplifier 2, and correspondingly adjust the gain of amplifier 2 via adjust signal 22.
As shown in
Differential amplifier circuit 34 may also include a pair of capacitors 46A and 46B coupled between transistors 44A and 44B. Capacitors 46A-46B may operate as a filter, e.g. a high-pass filter. In the depicted example of
Differential amplifier stage 4 may also include current source circuit 36. Current source circuit 36 may supply a substantially constant current to differential amplifier stage 4. The substantially constant current may act as a bias for operation of transistors 42A-42B and 44A-44B of differential amplifier stage 4. Current source circuit 36 may include transistors 50A-50D, each of which include a gate coupled to one or more bias inputs 57. In the example of
Differential amplifier stage 4 may also include Miller compensation circuit 32. In the embodiment of
Differential amplifier stage 4 also includes active bias circuit 30. Active bias circuit 30 may include resistors 40A and 40B, each of which include a first terminal coupled to a positive power supply terminal (e.g. VDD), and a second terminal coupled to drain terminals of transistors 42A and 42B of Miller compensation circuit 32.
Differential amplifier stage 4 may generate respective first and second polarity signals 14A and 14B of a scaled differential signal, e.g. positive and negative polarity signals of a scaled differential output signal. A gain applied to a signal by differential amplifier stage 4 may not be selectively adjustable.
The examples of differential amplifier stage 4 of
Furthermore, the circuit diagram of
As shown in
Gain adjust stage 6A also includes variable resistors 64A and 64B. As shown in
Variable resistors 64A and 64B may be adjustable via input terminals 23A and 23B Input terminals 23A and 23B may be, for example, input pins on an integrated circuit device or printed circuit board. A resistance of variable resistors 64A and 64B may be adjusted by applying adjust signal 22 to input terminals 23A and 23B. In one example, adjust signal 22 is a voltage.
In the depicted example of
As shown in
In one example, attenuator 7A is a t-attenuator as depicted in
As depicted in
Attenuator 7B receives first and second polarity signals 17A and 17B. Similar to the attenuator example 7A of
In one example, a signal received at attenuation select inputs 24A and 24B is one or more voltages, where an amplitude of the one or more voltages is selectable to set a desired amount of gain adjustment by attenuator 7B. In one example, a voltage supplied to attenuation select input 24A has a different amplitude than a voltage applied to attenuation select input 24B, and a difference between the amplitude of voltages at inputs 24A and 24B is selectable to set a desired amount of gain adjustment by attenuator 7B. Attenuator 7B may output first and second polarity signals 18A and 18B of an adjusted scaled differential signal that define a substantially constant impedance, regardless of a signal at attenuation select terminals 24A and 24B.
Due to the arrangement depicted in
A second end of resistors 76 and 77 are coupled to respective first and second ends of resistor 78. A second end of resistors 76 and 77 are also coupled to a first end of resistors 78 and 79. As depicted in
Resistors 78 and 79 each include respective second ends. The respective second ends may output respective first and second polarity signals 18A and 18B of an adjusted scaled signal. Resistors 76, 77, 78, 79, and 81 may operate as a voltage divider and thus attenuate a signal at inputs 19A and 19B and output an adjusted scaled differential signal 18A″ and 18B″. A level of amplitude adjustment of attenuator 80 may be selected by an input signal to variable resistor 81, e.g. adjust signal 22.
Various embodiments of the invention have been described. These and other embodiments are within the scope of the following claims.
Claims
1. An amplifier device, comprising:
- a differential amplifier gain stage that receives an input signal and applies a gain to the input signal to generate a scaled signal; and
- a gain adjust stage that receives the scaled signal and an adjust signal and adjusts an amplitude of the scaled signal based on the adjust signal and outputs an adjusted scaled signal, wherein the adjusted scaled signal has a substantial constant impedance regardless of a value of the adjust signal.
2. The device of claim 1, wherein the gain adjust stage outputs the adjusted scaled signal at a substantially constant impedance regardless of a magnitude of the input signal.
3. The device of claim 1, wherein the gain adjust stage comprises a source follower circuit.
4. The device of claim 3, further comprising:
- at least one variable resistor coupled to the source follower circuit, wherein the at least one variable resistor has a selectable resistance based on the adjust signal.
5. The device of claim 1, wherein the gain adjust stage includes an attenuator circuit
6. The device of claim 5, wherein the attenuator circuit is a pi-attenuator circuit.
7. The device of claim 5, wherein the attenuator circuit is a T-attenuator circuit.
8. The device of claim 5, wherein the gain adjust stage further includes a source follower circuit.
9. A method, comprising:
- receiving, at a differential amplifier stage, an input signal;
- scaling, by the differential amplifier stage, the input signal to generate a scaled signal;
- receiving, at a gain adjust stage, the scaled signal receiving, at the gain adjust stage, an adjust signal;
- adjusting an amplitude of the scaled signal by the gain adjust stage;
- outputting an adjusted scaled signal, wherein the adjusted scaled signal has a substantially constant impedance regardless of a value of the adjust signal.
10. The method of claim 9, wherein outputting the adjusted scaled signal includes outputting at a substantially constant impedance regardless of a magnitude of the input signal.
11. The method of claim 9, wherein outputting the adjusted scaled signal includes outputting by a source follower circuit.
12. The method of claim 11, wherein adjusting an amplitude of the scaled signal includes adjusting the amplitude based on a resistance of at least one variable resistor coupled to the source follower circuit.
13. The method of claim 11, wherein adjusting an amplitude of the scaled signal includes adjusting the amplitude by at least one attenuator circuit coupled to the source follower circuit.
14. The method of claim 9, wherein adjusting the amplitude of the scaled signal includes adjusting the amplitude by an attenuator circuit.
15. The method of claim 14, wherein adjusting the amplitude by an attenuator circuit includes adjusting the amplitude by a pi-attenuator circuit.
16. The method of claim 14, wherein adjusting the amplitude by an attenuator circuit includes adjusting the amplitude by a T-attenuator circuit.
17. A device, comprising:
- means for scaling an input signal to output a scaled signal;
- means for receiving the scaled signal and an adjust signal;
- means for adjusting an amplitude of the scaled signal based on the adjust signal; and
- wherein the means for adjusting an amplitude of the scaled signal output an adjusted scaled signal with a substantially constant impedance regardless of a value of the adjust signal.
18. The device of claim 17, wherein the means for adjusting an amplitude of the scaled signal include an attenuator circuit
19. The device of claim 17, wherein the means for adjusting an amplitude of the scaled signal include a source follower circuit and at least on variable resistor.
20. The device of claim 17, wherein the means for adjusting an amplitude of the scaled signal include a source follower circuit and an attenuator circuit.
Type: Application
Filed: Jan 27, 2010
Publication Date: Jul 28, 2011
Patent Grant number: 8085091
Applicant: Honeywell International Inc. (Morristown, NJ)
Inventors: Said Abdelli (Minneapolis, MN), Jeffrey Kriz (Eden Prairie, MN)
Application Number: 12/694,734
International Classification: H03F 3/45 (20060101);